1. Field of the invention
The invention pertains to a retractable medical device which in the preferred embodiment is useful for collecting body fluids from a patient. It is primarily useful as a blood collection device.
2. Background of the Prior Art
Prevention of needle sticks has become a paramount concern of the healthcare industry because of serious and deadly risk factors associated with AIDS and other serious communication diseases. Blood collection devices utilize a needle inserted into a patient's vein so as to draw blood through the needle into an associated separate collection reservoir. Accidental needle sticks from previously used needles can occur during the fluid withdrawing process and subsequent handling and disposal operation. Until such used medical devices are destroyed, they remain potentially lethal.
Illustrative of the type of device used for blood sampling is a collection device sold under the trademark Vacutainer® by Becton Dickinson Corporation, which has been the conventional standard for this type of device. It has a tubular syringe-like body with a needle in the front end, part of which extends back into a tubular syringe-like shell. Part of the needle extends externally for punching the skin. An evacuated collection tube with a rubber stopper is placed into the open back of the syringe-like shell with the rubber stopper against the internal end of the needle. After the skin is punctured, the collection tube is pushed forward to cause the needle to enter the evacuated tube. Vacuum helps draw blood into the collecting tube. When a sufficient sample has been obtained, the collecting tube and the stopper are simply withdrawn from the tubular shell and sent to the laboratory. This particular device has a permanently extended needle and an opening in the back for the collection tube which remains open after the collection tube is removed, leaving small quantities of blood and an internally exposed needle.
Retractable medical devices which are used for collecting fluid samples from patients are known. While they offer retraction of the needle, they suffer from high manufacturing and assembly cost. They lack simplicity which results in a multiplicity of difficult to manufacture and assemble parts. An early example of such a device is Haber U.S. Pat. No. 4,813,426 which employs a mechanically translatable insert holding a double-ended needle. It has a position which compresses a spring portion of the holder. When buttons extending from opposite sides of the outer tube are compressed, the needle carrier can be mechanically moved to the position of us or to a rearward safe position. Allard U.S. Pat. No. 4,838,863 describes a spring loaded double ended needle carrier in a T-shaped housing having an opening behind for the sample tube. The needle holder is locked in a use position with a removable pin which is withdrawn to retract the needle. Alternately, breakable tabs on the needle holder extend laterally under a shelf with pins which may be pushed down when the sample tube is inserted to fracture the breakable tabs thereby releasing the needle holder which is withdrawn into the interior as the sample tube is removed. Subsequently, a cap is provided to close the back. Allard does not explain how one could assemble the device without making the outer body in two or more pieces.
In addition, a number of devices attach the double ended needle to a partially withdrawable plunger with an opening in back for the sample tube. Shaw U.S. Pat. No. 5,423,758 discloses a tubular outer body with a partially removable plunger. The plunger has a separable needle holding portion for a double ended needle and an opening in the back of the plunger for a sample tube. It utilizes a two position end cap from which the sample tube extends. The plunger is used to position and retract the needle assembly.
By in large, the prior art fails to take into account the need for a single one-handed required and controlled action that will simultaneously close the back of the main body of the device and initiate retraction of the exposed needle after the sample tube is removed. If the inner needle which punctures the collection tube is not covered with a rubber sheath, blood will continue to flow into the device. This blood provides a source of contamination during subsequent handling of the device. If the internal needle is covered with a rubber sheath to prevent the blood from continuing to flow after the collection tube is removed, the rubber sheath serves to hide a sharp needle which can result in unintended punctures. Since the sheathed needle looks safe, people tend to put their finger into the open end without thinking. Even if a cap were to be provided, it use requires a separate operation and it is easy to forget or simply fail to use it. Consequently, an improvement in safety is possible with a device that caps the back of the device while it is retracting.